Osselets refers to swellings that appear along the front and sides of the ankle joint, in the area just below the cannon bone. Osselets are commonly seen in young horses that are broken early and used hard. They usually represent strain and micro tearing of the attachment of the fetlock/ankle joint capsule to the cannon bone. This is usually accompanied by synovitis. However, small chip fractures may also be present — which may be a form of OCD in the ankle — so it’s always wise to have radiographs taken of a horse with osselet-type swellings. If large enough, it may be decided the chip or chips need to be removed. The sooner this is done, the better. A horse with osselets may or may not appear to be sore, but flexion tests are generally positive and it’s possible to feel locally increased temperature, “heat,” in most cases.
For osselets not complicated by chips, the same therapy as described for synovitis is usually indicated. Stall rest or hand walking only is indicated until the inflammatory response has quieted down (usually in about three days), after which light work may be resumed but nothing heavy enough to cause increased swelling and heat again. The controlled exercise should continue for four to six weeks before attempting to increase the work load. Icing for an hour after each exercise session is helpful in preventing any relapse to increased inflammation.
When caught and treated early, the swelling from osselets may resolve entirely. Many horses, though, are left with some permanent residual thickening.